liquefaction pathways of bituminous subbituminous coals andtheir

More documents

Recommendations

Info

Will simple lumped mass balance expressions be found for U(t). For example, at temperatures 360 OC and below, the rate is first-order with rate coefficients, k , independent of x and identical for the extractable groups. For this case it is straightforward to demonstrate that the lumped rate is first-order with rate coefficient equal to ko: thus, and u(x.t) = ko co(x) exp(-kot)/Q (16) u(t) = ko Co exp(-kot)/Q (17) which can be compared with the lumped reactor exit concentration. Experiments The experimental apparatus and procedure have been described previously (Zhang et al., 1992). Supercritical fluid thermolysis of Illinois No. 6 coal is conducted in a fixed-bed reactor with flowing solvent. The lumped, reactor-exit concentration is measured by spectrophotometric absorbance in a flow cuvette. Thus we select t- butanol as the solvent, since it does not interfere with the uv absorbance of aromatic coal extraction products. The thermolysis process is carried out at constant pressure, 6.8 MPa, and constant flow rate, 0.17 cm3/sec. Coal particles are small enough that intraparticle diffusion resistance is not significant, and the solvent flow rate is large enough that external mass transfer resistance is negligible (Zhang et al., 1992). The coal is pretreated by supercritical extraction at 300 OC to remove physically extractable constituents. Coal extract samples of 100 ml were collected during the thermolysis process, and concentrated by evaporation of t-butanol under vacuum. The MWDs of these samples, based on polystyrene molecular-weight standards, are determined by gel permeation chromatography with the uv detector set at 254 nm (Bartle et al. 1984). Discussion of Results The time evolution of extract MWDs for the temperatures 340 and 360 OC are provided in Figures 1. The two temperatures show MWDs whose shapes are similar at the different times, i.e., the ratio of peak heights, the position of peaks, and the average molecular weight are invariant with time. Such behavior can be described by assuming that the rate coefficient for the MWDs is independent of MW. The values of the first-order rate coefficients at the two temperatures, displayed in Table 1, give an energy of activation El = 58 kJ/mol. The gamma distribution parameters, provided in Table 2, show that increasing the temperature changes only the zero moments. The concentrations for each group of extractable compounds, moi, shift due to the greater extraction at the higher of the two temperatures. The comparison of the calculated and experimental MWDs is shown in Figure 2 for two samples. Only time changes during the course of the evolution of the MWDs; the parameters for the initial MWD in the coal and the rate coefficients are constant. The agreement between the experimental data and the model calculations is consistently good for a samples during the course of a run. Figure 3 shows experimental data for total, lumped extract concentrations for the thermolytic extractions at two temperatures. The lumped concentrations are determined by the flow-through spectrophotometer at the reactor exit. The model calculations shown in Figure 3 are based on Eq. (17) and the same rate constant values (Table 1) determined from the time evolution of the mDs. The 642
satisfactory agreement between theory and experiment, for both the lumped and MWD data, supports the validity of the explanation of coal thermolytic extraction that we have proposed. conclusion A continuous-flow thrmolysis reactor, in which supercritical t- butanol contacts a differential bed of coal particles, provides sequential coal-extract samples that are analyzed by HPLC gel permeation chromatography to obtain time-dependent MWD data. The coal thermolysis experimental data support an interpretation of the results based on considering the molecular weight of extraction products as a continuous variable. This continuous-mixture theory suggests that three groups of coal components are extracted independently. At temperatures 340 OC and 360 OC the MWDs maintain a similar shape during the semibatch extraction. This indicates that first-order kinetics dominate, and that the rate coefficient is independent of molecular weight. The lumped extract concentration is monitored at the reactor exit by continuous uv-absorbance spectrophotometry. Both MWD and lumped concentration data are described by consistent expressions based on the same rate coefficient . Acknowledgements The financial support of Pittsburgh Energy Technology Center Grant No. DOE DE-FG22-90PC90288, and the University of California UERG is gratefully acknowledged. References R. Aris, I8Reactions in Continuous Mixtures," AIChE J. 35, 539 (1989). Abramowitz, M. and I. A. Stegun, Handbook of Mathematical Functions, NBS, Chap. 26 (1968). Bartle, K. D., M. J. Mulligan, N. Taylor, T. G. Martin, C. E. Snape, "Molecular Mass Calibration in Size-Exclusion Chromatography of Coal Derivatives," Fuel, 63, 1556 (1984). Darivakis, G. S., W. A. Peters, J. B. Howard, "Rationalization for the Molecular Weight Distributions of Coal Pyrolysis Liquids,'* AIChE - J. 36, 1189 (1990). Ho, T. C. , R. Aris, "On Apparent Second-Order Kinetics," AIChE J. 33, 1050 (1987). Zhang, C., J. M. Smith, B. J. McCoy, "Kinetics of Supercritical Fluid Extraction of Coal: Physical and Chemical Processes,*f ACS SvmDosium on SuDercritical Fluids, in press (1992). 643
Page 1 and 2:
LIQUEFACTION PATHWAYS OF BITUMINOUS
Page 3 and 4:
the conversion of A+P and O+G with
Page 5 and 6:
Asphaltcncs PrCasphaltenCS Cwr%, da
Page 7 and 8:
NEW DIRECTIONS TO PRECONVERSION PRO
Page 9 and 10:
ecause of incorporation of the coal
Page 11 and 12:
should be considered more. The step
Page 13 and 14:
17 18 Run no. 0 cys I ToS-CyS TS-To
Page 15 and 16:
INTRODUCTION Effects of Thermal and
Page 17 and 18:
apid decline in modulus. The loss m
Page 19 and 20:
-0.01- . 04 5 -0.03- E 6 -0.0s- c)
Page 21 and 22:
Assessment of Small Particle Iron O
Page 23 and 24:
yields are calculated by subtractin
Page 25 and 26:
conversion is greater than the corr
Page 27 and 28:
Table 3. Effect of Superfine Iron O
Page 29 and 30:
EFFECT OF A CATALYST ON THE DISSOLU
Page 31 and 32:
inherent volatility of Mo(CO), perm
Page 33 and 34:
Analysis of the quantity and compos
Page 35 and 36:
$ EO .- 0 m L 0 c 0 0 > 40 300 350
Page 37 and 38:
0 0 0 0 0.000 0.005 0.010 0.015 0.0
Page 39 and 40:
of these studies indicate that cont
Page 41 and 42:
Different levels of adsorption occu
Page 43 and 44:
Nominal 2 Table 1. Concentration of
Page 45 and 46:
- iF m 1.6 1.4 1.2 - - - 1- 0 0.8 -
Page 47 and 48:
RESULTS AND DISCUSSION Swelling of
Page 49 and 50:
. . % . . 9 'HF 0 0 0 *. . 0 . . 0
Page 51 and 52:
1.50 KQ 1.00 0.50 I / ' 02 525 I 1
Page 53 and 54:
hydrogen atoms. The hydrogen atoms
Page 55 and 56:
D to generate more D atoms. It is r
Page 57 and 58:
12. a. Poutsma, M. L.; Dyer, C. W.
Page 59 and 60:
Figure 3. Minimum Steps to Explin D
Page 61 and 62:
Apoaratus and Procedure Microflow R
Page 63 and 64:
Model ComDound Test Figure 5 shows
Page 65 and 66:
Figure 1. High resolution gas chrom
Page 67 and 68:
Figure 5. Product distribution for
Page 69 and 70:
THQ at somewhat higher temperatures
Page 71 and 72:
areas of the particles and the SEM
Page 73 and 74:
Experimental Catalyst Precursors an
Page 75 and 76:
impregnating solvent. Table 3 shows
Page 77 and 78:
of MoCo-TC2 at the level of 0.5 wt%
Page 79 and 80:
Table 4. Effect of Temperature Prog
Page 81 and 82:
In the past, chemical treatments in
Page 83 and 84:
The effect of Corn20 preaatment on
Page 85 and 86:
Reaction Time Figure 1 - Schematic
Page 87 and 88:
DISSOLUTION OF THE ARGONNE PREMIUM
Page 89 and 90:
A much more def~tive trend is seen
Page 91 and 92:
EFFECT OF CHLOROBENZENE TREATMENT O
Page 93 and 94:
same conditions and an extraction t
Page 95 and 96:
ACKNOWLEDGEMENT The authors thank t
Page 97 and 98:
THE STRUCTURAL &=RATION OF HUMINlTE
Page 99 and 100:
to be originally derived from demet
Page 101 and 102:
145 30 I --/---Jh I , , I I , 250 2
Page 103 and 104:
THE EFFECTS OF MOISTURE AND CATIONS
Page 105 and 106:
1 for the Zap lignite. These result
Page 107 and 108:
content of the samples ion-exchange
Page 109 and 110:
Table 1. F'yrolysis Results of Vacu
Page 111 and 112:
585 I
Page 113 and 114:
EFFECT OF TEMPERATURE, SAMPLE SI2E
Page 115 and 116:
of some of the thermobalance runs.
Page 117 and 118: 2. The mechanism of drying is a uni
Page 119 and 120: Influence of Drying and Oxidation 0
Page 121 and 122: "c gives W conversion mpared to the
Page 123 and 124: Table 1. Products dismbutions (dmmf
Page 125 and 126: - 50 45 40 E 35 2 30 E T) 25 ap 20
Page 127 and 128: Influence of Drying and Oxidation o
Page 129 and 130: FTIR . . of the L m To investigate
Page 131 and 132: CONCLUSIONS The characexizntion of
Page 133 and 134: A b S 0 r b a n C e A b s 0 r b a n
Page 135 and 136: An NMR Investigation of the Effd of
Page 137 and 138: for determining the area of the pea
Page 139 and 140: of the ronl roniponcnte nnd (2) the
Page 141 and 142: 2w 180 160 9 140 120 P loo f 80 P O
Page 143 and 144: 25 I 20 ' + 0 Drying lime, hours Fi
Page 145 and 146: substructure have been identified a
Page 147 and 148: Pyridine extraction showed that 60
Page 149 and 150: Figure 1. Reflected white-light pho
Page 151 and 152: Table 3. Pyridine Extraction Sample
Page 153 and 154: A bang-bang control strategy was us
Page 155 and 156: increased from 120°C to 135”C, r
Page 157 and 158: * wt% based on the amount of naphth
Page 159 and 160: Use of Biocatalysts for the Solubil
Page 161 and 162: Results Enzyme Modification with Di
Page 163 and 164: Conclusions Reducing enzymes can be
Page 165 and 166: Dynamics of the Extract Molecular-W
Page 167: where yi = (x-xi !/pi. The zero mom
Page 171 and 172: 0.8 0.6 0.4 0.2 “E \ bo Y, - 1 0
Page 173 and 174: The Use of Solid State C-13 NMR Spe
Page 175 and 176: differences lie in the fact that th
Page 177 and 178: I- z W 0 K W n PROTONATED AROMATIC
Page 179 and 180: ZAP WIO SIDE CHAINS IN PYRIDINE EXT
Page 181 and 182: ORGAFlIC VOLATILE MATER AND ITS SUL
Page 183 and 184: (Figure 1). They indicated that the
Page 185 and 186: Table 3. Elemental analysis of arom
Page 187: 1- 700'C Figure 3. GClFID chromatog
show all

liquefaction pathways of bituminous subbituminous coals andtheir

Create successful ePaper yourself

Delete template?

Save as template?